This invention relates to testing apparatus and methods.

International Patent Application Publication W092/22796 discloses a scale modelling centrifuge which has a rotary circular base wall, which may form part of a drum, possibly with a detachable peripheral wall either carrying an annular sample-receiving trough or constituted by such trough, or which may have mounted therearound a plurality of sa ple- receiving containers. The circular base wall may be mounted by way of a co-axial hollow axle in external bearings, the axle and thus the base wall being rotated by an electric motor via a belt-and-pulley system. Mounted co-axially within the axle by way of bearings internal of the axle is a shaft carrying a work support. The shaft and thus the work support are rotatable by a second electric motor through a second belt-and-pulley system. Fixed to the axle and the shaft are respective sets of slip rings whereby control et cetera signals may be transmitted to and from various detecting devices (for pressure, displacement et cetera) in rotating, scale-modelling samples supported by the base wall and to and from apparatus on the rotating work support.

Such drum may receive at its internal periphery a plurality of arcuate troughs connected via respective links, passing through respective circumferential slots in the drum, to respective rollers connected to the circumferential wall of the drum by way of respective arms. The links are articulated to the troughs and to the rollers, whilst the arms are articulated to the rollers and the drum. Encircling the drum co-axially is a fixed, cam track of a sinusoidal form. Upon rotation of the drum, the cam track and the rollers cause the troughs to perform a sinusoidal wave motion to simulate the effect of an earthquake in soil, scale-modelling samples in the troughs. By way of the links, the rollers push the troughs tangentially relative to the drum, so imparting a circumferential oscillation to the troughs to simulate the effect of an earthquake.

In another version disclosed in W092/22796 the troughs

are replaced by an annular channel containing the soil, and the rollers and cam track are replaced by horizontal, annular brake flanges of the drum and pairs of hydraulically-operated brake shoes regularly spaced around the drum. Pulsed application of the brake shoes to the flanges produces an earthquake effect circumferentially in the soil.

In two other versions disclosed therein, the earthquake-simulating system is contained within the drum. In one version, the soil is contained in an annular channel mounted between pairs of upper and lower hydraulic rams operating circumferentially of the drum. An elastomeric annulus may be interposed between the channel and the drum to support the channel radially relative to the drum. The base wall of the drum is relatively massive, to give the drum a high reaction mass to minimize transmission through the drum of the circumferential oscillation motions produced by the rams. In the other version, the soil sample is contained in a first trough mounted within a second trough by way of a pair of hydraulic rams arranged to oscillate the first trough relative to the second. The second trough is itself mounted upon the internal peripheral surface of the drum by way of pairs of upper and lower hydraulic rams acting circumferentially of the drum. The rams mounting the first trough can be programmed to operate independently of those mounting the second trough, simultaneously to impart to the soil oscillations in two senses, namely radially and circumferentially. The programme can be such that the rams operate in phase relationship the same as that of the earthquake wave pattern which it is desired to simulate. Such assembly of troughs, rams and soil is one of at least two equal masses regularly distributed around the internal peripheral surface of the drum to ensure dynamic and static balance of the drum about its axis, whereby the vector sum of forces at the drum centre will be zero. The sub-assembly of the first trough and its mounting rams is one of a corresponding number of equal sub- masses included in the equal masses. These sub-masses are so oscillated radially of the drum by pairs of rams that the

vector sum of the radial forces at the drum centre will be zero .

According to a first aspect of the present invention, there is provided a drive system for a testing apparatus , comprising first and second drive shafts substantially co¬ axial with each other, and first and second driving means connected to the respective shafts for rotating the same independently of each other , characterised by first and second readily releasable connecting means at respective ad j acent ends o f the re spect ive sha ft s and whe reby re spect ive piece s o f equ ipment from a range o f t e st equipment can be readily releasably connected t o the respective shafts for rotation thereby .

According to a second aspect of the present invention, there is provided a method comprising selecting first and second pieces of equipment from a range of test equipment, readily releasably attaching said first and second pieces to respective adjacent ends of first and second drive shafts substantially co-axial with each other, rotating the shafts independently of each other thereby to rotate said first and second pieces independently of each other, readily detaching said first piece from the first drive shaft , selecting a third piece o f equipment from said range , and readi ly releasably attaching said third piece to such adjacent end of the first drive shaft .

Owing to these aspects of the invention, it is possible to employ a variety of pieces of test equipment in a single basic apparatus, thus avoiding the need to provide separate basic apparatuses for various test purposes . For example, the testing apparatus may be in the character of a drum centrifuge, an arm centrifuge, or an apparatus for studying the shear properties of fluids . In the event that the apparatus is of the character of a drum centrifuge, the relevant end o f the outer of the first and second drive shafts may have readily releasably connected thereto a drum which may carry a scale modelling sample to be tested and the relevant end of the inner shaft may have one or more robot mechanisms readily releasably connected thereto . The robot mechanism ( s ) may serve to support test pieces , or

measuring or detecting instruments, for example. In the event that the apparatus is of the character of an arm centrifuge, the outer shaft may have readily releasably connected thereto a rotary inertial mass, or a rotary shield, for example, whilst the inner shaft may have readily releasably connected thereto an arm which may carry a scale modelling sample to be tested and also measuring or detecting instruments, for example. In the event that the testing apparatus is employed in determining shear in fluid, the inner and outer shafts may have readily releasably connected thereto respective inner and outer concentric drums whereof the respective circumferential walls are of an arrangement of co-axial stationary and rotary walls, the relative rotation of which produces shear in fluid therebetween .

Although the first and second drive shafts are rotatable independently of each other, they may also be rotatable in dependence on each other, such as in unison.

According to a third aspect of the present invention, there is provided earthquake-simulating apparatus comprising carrying means movable along a path for carrying a scale modelling sample, mounting means mounting said carrying means in such manner that said carrying means is oscillatable, and supporting means relative to which said carrying means moves along said path, characterised by a shearing arrangement comprising holding means on one of said carrying means and said supporting means for holding a shearable member and shearing means on the other of said carrying means and said supporting means for shearing said shearable member as said carrying means moves along said path relative to said supporting means, thereby to cause oscillation of said carrying means.

According to a fourth aspect of the present invention, there is a provided a method of simulating an earthquake, comprising moving oscillatable carrying means containing a scale modelling sample along a path relative to supporting means, utilising the kinetic energy of the moving carrying means to shear a shearable member, and utilising the reaction force of the shearing on the carrying means to

initiate oscillation of the carrying means.

Owing to these two aspects of the invention, it is possible to arrange that the shearing of the shearable member applies a sudden shock to the carrying means and thus the scale modelling sample, thereby simulating accurately the commencement of an earthquake.

Although the shearing of the shearable member could merely be such that it is permanently deformed, we believe that it is preferable that the member be cut into separate pieces by the shearing, since this should give the more accurate shock.

The earthquake-simulating apparatus may be of the character of a drum centrifuge or an arm centrifuge.

According to a fifth aspect of the present invention, there is provided earthquake-simulating apparatus, comprising a movable inert ial mass, movable carrying means oscillatable relative to said mass for carrying a scale modelling sample, and force-applying means serving to apply a force to said carrying means to initiate oscillation thereof relative to said mass, characterised by frictional clutch means between said carrying means and said mass and operable in such manner as to effect rapid decay of said oscillation.

According to a sixth aspect of the present invention, there is provided a method of simulating an earthquake, comprising drivingly connecting together an inertial mass and carrying means carrying a scale modelling sample, moving said mass and said carrying means, oscillating said carrying means relative to said mass, and operating frictional clutch means between said mass and said carrying means to effect rapid decay in the oscillation of said carrying means relative to said mass.

Owing to these two aspects of the invention, it is possible to effect rapid decay in the oscillation of the carrying means and thus of the scale modelling sample, thereby to simulate accurately the relatively sudden termination of an earthquake.

The operation of the frictional clutch means to effect rapid decay of the oscillation can consist of partial

disengagement to produce continuous slippage or of rapid disengagement and re-engagement, to dissipate kinetic energy from said mass in said clutch means.

Again, the earthquake-simulating apparatus can be of the character of a drum centrifuge or an arm centrifuge.

According to a seventh aspect of the present invention, there is provided scale modelling apparatus comprising rotary carrying means for carrying a scale modelling sample, and rotary supporting means for rotating with said carrying means, characterised by a torsion member of resilient material by way of which said carrying means is connected to said supporting means so as to be oscillatable relative to said supporting means.

Owing to this aspect of the invention, the scale modelling apparatus can be of a simplified construction.

According to an eighth aspect of the present invention, there is provided earthquake-simulating apparatus comprising carrying means for carrying a scale modelling sample, supporting means, and resilient means by way of which said carrying means is connected to said supporting means so as to be oscillatable relative to said supporting means, the arrangement being such that, in use, the frequency of oscillation of the carrying means relative to the supporting means is a number of cycles per second approximately equal to the ratio of full-scale to the scale of said sample.

Owing to this aspect of the invention, small scale simulation of a full scale earthquake is obtained. If the frequency of oscillation in a typical earthquake is about 1 cycle per second, then, in a model test at a scale of 1/300, the model would be shaken at 300 cycles per second. To attain relatively high frequencies (of over 100 cycles per second) the resilient means is a spring/mass combination, with the spring advantageously being a torsion spring or a leaf spring. In order that the invention may be clearly understood and readily carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:-

Figure 1 shows a vertical axial section through a drive system of a testing apparatus,

Figure 2 shows a plan view of the system, Figure 3 is a view similar to Figure 1 but also showing test equipment of the apparatus, the equipment having been selected from a range of test equipment, Figure 4 is a plan view of the apparatus of Figure 3,

Figure 5 is a view similar to Figure 3, but showing the apparatus with other equipment selected from the range,

.Figure 6 is a plan view of the apparatus according to Figure 5, and Figure 7 is a view similar to Figure 3, but showing the apparatus with further equipment selected from the range.

Referring to Figures 1 and 2, the apparatus includes a steel base structure 1 including a central vertical tube 2 in which are independently rotatably mounted co-axially inner and outer vertical hollow shafts 3 and 4 including at their upper ends respective horizontal flanges 5 and 6. The outer shaft 4 is rotatably mounted in the tube 2 by way of upper and lower bearings 7 and 8, whilst the shaft 3 is rotatably mounted in the shaft 4 by way of upper and lower bearings 9 and 10. Secured to the respective lower end zones of the shafts 3 and 4 are pulleys 11 and 12 driven by respective electric motors 13 and 14 through respective timing belts 15 and 16. Between the pulleys 11 and 12 is an electrically operable friction clutch 17 whereby the pulleys can be drivingly interconnected. The motors 13 and 14, which are fixed to the base structure 1, are controlled independently of each other, whereby the shafts 3 and 4 can be rotated selectively independently of each other or in a desired relationship to each other, for example in unison. The flanges 5 and 6 are provided with respective rings of through bores 18 and 19 whereby various pieces of equipment selected from the range of test equipment can be firmly, but readily releasably, attached thereto. Some of these pieces from the range are shown in Figures 3 to . Yet further pieces from the range may be fixed to the base structure 1, again as shown in Figures 3 to 7. A hole 20 provided in the top wall of the base structure 1 permits the mounting on the structure 1 of a lifting mechanism for enabling an operator to handle the various pieces from the range during

connection to and disconnection from the flanges 5 and 6 and the base structure 1.

Referring to Figures 3 and 4, there is readily releasably connected to the flange 6 (by nut-and-bolt devices which are not illustrated but which extend through the holes 19) a drum 30 containing a scale modelling sample 31, for example a slurry. Mounted upon the drum 30 are electrical signal conditioning devices 32 and slip rings 33 associated with measuring and detecting instruments (not shown) at the sample 31. Readily releasably attached to the flange 5 (by nut-and-bolt devices which are not shown but which extend through the holes 18) is a robot mechanism 34. In the example illustrated, the mechanism 34 is hydraulic and includes an hydraulic piston-and-cylinder device 35 connected by hydraulic lines, which extend through the shaft 3, to hydraulic slip rings 36. Readily releasably fixed to the base structure 1 (again by nut-and- bolt devices not illustrated) is an annular safety shield 37 encircling the drum 30. Also readily releasably fixed to the base structure 1 is a ring 38 encircling the annular space 39 between the drum 30 and the structure 1 and enabling air pressurisation of that space to deter ingress of foreign matter to that space.

Referring to Figures 5 and 6, the drum 30, the mechanism 34 (with its associated hydraulic lines and hydraulic slip rings 36) and the ring 38 have been readily disconnected from the shafts 6 and 5 and the base structure 1, respectively, and there have been connected to the flanges 5 and 6 by the nut-and-bolt devices a centrifuging arm 40 and a massive inertial disc plate 41, respectively.

At one end of the arm 40 is a carrier 42 for a scale modelling sample (not shown) , whilst at the other end of the arm 40 is a counter-balancing mass 43. The apparatus is being employed to simulate earthquakes. For that purpose, the motor 14 is not required and is therefore not shown, although it is still present. Fixed to the radially outer part of the carrier 42 is a block 44 which holds firmly a shearable metal plate 45. Pivotably mounted upon the shield 37 is a shearing abutment 46 which, by means of an

hydraulic piston-and-cylinder device 47 can be swung into and out of the path of movement of the shearable plate 45 . In use, the motor 13 rotates the shaft 4 and, by way of the clutch 17 , the shaft 3 in unison, so that the arm 40 and the plate 41 rotate in unison . At a desired speed of rotation of the items 40 and 41 , the abutment 46 is swung into the path of the plate 45 and shears off part of the plate 45 , that shearing giving a sudden shock to the carrier 42 and thus the arm 40 and thereby dragging the arm 40 slightly back relative to the plate 41 . This puts the shaft 3 into torsion and, via the clutch 17 , the shaft 4 al s o into torsion . The shafts 3 and 4 are of a material of high stiffness . The shear modulus of the shaft material is advantageously higher than that of steel . As the arm 40 and the plate 41 continue to rotate, the torsional forces cause the arm 4 0 to oscillate at a frequency of , for example, 300 cycles per second about the axis of the shafts 3 and 4 , so simulating an earthquake at the carrier 42 . When it is des ired to simulate the terminat ion of such earthquake, the clutch 17 is operated in such a matter that the torsional forces are dissipated rapidly . The operation of the clutch may be such that while the clutch is in a part ial ly di sengaged condit ion, the result ing slippage produces friction which dissipates the torsional energy of the shafts . Alternatively , the clutch may be rapidly disengaged and re-engaged a number of times , thereby again frictionally to dissipate the torsional energy .

In other words, the energy stored in the massive plate 41 is employed to shear the plate 45 and the reaction force thereby produced twists the shafts 3 and 4 . The energy stored in the shafts 3 and 4 causes a strong "earthquake" vibration of the sample during which the shaft 3 remains securely connected to the shaft 4 . When it is desired to end the scale earthquake after, say , 200 t o 300ms , the clutch 17 is operated and the energy stored in the shafts 3 and 4 thereby dissipated . When substantially all of the energy stored in the shafts 3 and 4 has been dissipated, the scale earthquake is over and the clutch 17 is re-engaged . We believe that the use of shearing to init iate the scale

earthquake enables scaled earthquake forces to be obtained in up to a 1/300 scale earthquake.

Referring to Figure 7, the arm 40 and the plate 41 have been readily disconnected and replaced by respective rotary drums 50 and 51. The shield 37 has also been readily disconnected and replaced by a shield 52 supporting an annular wall 53 extending between the annular circumferential walls 54 and 55 of the drums 50 and 51, but for only part of the height of those walls. The central bore 56 of the shaft 3 serves for the supply of a liquid, e.g. oil or drilling mixtures, for example of muds and chippings, shearing properties of which are to be studied. The liquid entering through the bore 56 flows radially outwardly through between the drums 50 and 51 and then vertically upwardly between the walls 54 and 55. The annular stream of liquid then divides into an inner annular branch stream between the walls 53 and 54 and an outer annular branch stream between the walls 53 and 55. If the drums 50 and 51 are being driven in contra-rotation by the respective motors 14 and 13, the liquid in the main stream between the walls 54 and 55 is subjected to very high shear, whilst the liquid in the branch streams between the walls 53 and 54 and the walls 53 and 55 is subjected to significantly lower shear. If the speeds of rotation of the drums 50 and 51 are significantly different from each other, significantly different shears are obtained in the two branch streams. By means of instrumentation (not shown) these shear effects are detected and measured. The character of the flow can be studied and the shear properties of the fluid can be deduced. For relative rotation of the walls 54 and 55, the clutch 17 is naturally in a disengaged condition.