Undeformed Shape Research Articles

Low Frequency Vibration Assisted Drilling of Aluminium Alloys

In the present study the vibration drilling process of light weight materials and compound stacks has been investigated. Fiber-metal compound materials provide excellent mechanical properties which make them a major choice in lightweight applications. Especially in aircraft industry the use of multi-layer materials is significantly increased during the last few years. To join parts of dissimilar materials usually rivets or bolts are applied as fasteners. Therefore it is necessary to machine boreholes with partially very high quality requirements. Because of the different material properties the machining process of serial stacks imposes high demands to the cutting tools and requires certain process strategies. Previous investigations revealed that the bore surface can be damaged during the extraction of the hot and sharp metallic chips. Besides the risk of thermal damage the main issue lies in an erosive expansion of the borehole diameter due to the reaming of metallic chips at the borehole surface. The chip extraction can be significantly improved by low frequency assisted vibration drilling. In that case the axial tool movement is superimposed by a sinusoidal oscillation (in this case 1.5 per revolution) which is provided by the tool holder. Under certain cutting conditions this leads to a controlled chip breakage. Compared to conventional drilling the process parameters, cutting speed vc and feed f are supplemented with the amplitude A of the oscillation and the frequency f which represents the amount of vibrations per revolution of the tool. This causes radical changes to the kinematics of the process and therefore of the cutting conditions and chip formation. For a better understanding of the process a kinematic model for a two-flute cutter was developed which allows calculating the undeformed chip shape in dependency of the four cutting parameters vc, fz, A and f. The model also helps to predict whether a discontinuous cut will be achieved or not. To characterize the process and chip shape the following parameters are optionally calculated within the model: maximum chip thickness, chip radian, effective feed, feed speed at the moment of tool entrance and exit (for one chip). Experimental drilling trials in Al2024 T351 were used to evaluate the calculated parameters. The chip thickness and radian as well as the cutting time show a very good correlation to the calculations. It is interesting that the measured cutting forces are much lower compared to the theoretical values according to the Kienzle cutting force equation. Additionally it was found that the measured cutting force is strongly decreasing with an increasing cutting speed. Infrared images of the drilling process in Ti6Al4V were used to analyze the temperature close to the cutting zone and to observe the chip evacuation during the process. It was found that the cutting temperature is up to 50% lower when using vibration drilling. Furthermore it was shown that this effect is strongly dependent on the chip extraction. It is important that the chips do not stack in the drilling flute during the process. A chip breakage is facilitated by a decreasing ratio between feed and amplitude. At the same time an increasing material removal rate degrades the chip extraction even if the chips are separated. Besides the advantages of vibration drilling a major issue was found to be chipping at the cutting edges or even tool breakage. This could be avoided by a reduction of the oscillation amplitude and /or feed. Under consideration of these correlations the productivity of the drilling process and the bore hole quality in CFRP/Ti6Al4V-stacks could be significantly increased. The investigations have shown that vibration assisted drilling represents a huge opportunity, especially in the field of drilling composite materials. However further investigations are necessary to better understand this very complex process.

Orbital drift of capsules and red blood cells in shear flow

Many numerical studies have considered the dynamics of capsules and red blood cells in shear flow under the condition that the axis of revolution of such bodies remained aligned in the shear plane. In contrast, several experimental studies have shown that the axis of revolution of red blood cells could drift away from the shear plane in a certain range of controlling parameters. In this article, we present three-dimensional numerical simulations on the orientation dynamics of capsules in simple shear flow with different initial undeformed shapes, namely, prolate, oblate, and biconcave disk. It is observed that unlike rigid ellipsoids in Stokes flow, capsules reorient their axis of revolution either towards the vorticity axis while undergoing a precessing motion or towards the shear plane while undergoing a kayaking-type motion. The specific dynamics are observed to depend on initial shape, capillary number, and the ratio of the internal to external fluid viscosity. Near the physiological values of the viscosity ratio, the biconcave shape performs a rolling motion like a wheel. If the viscosity ratio is reduced below the physiological range, a transition to the kayaking dynamics is observed with increasing capillary number. The critical shear stress at which the rolling-to-kayaking transition occurs is found to be dependent on the viscosity ratio.

초탄성 형상기억합금을 활용한 좌굴방지 가새프레임 구조물의 지진거동 및 성능평가

최근에는 초탄성 형상기억합금을 구조물 일부에 설치하여 지진과 같은 외부 충격하중으로 인해 발생되는 영구적인 소성 변형을 줄이고 자동치유가 가능한 변위제어 시스템을 개발하는 연구가 활발하게 진행되고 있다. 초탄성 형상 기억합금은 상당량의 변위를 가하더라도 별도의 열처리 없이도 상온에서 단지 하중만을 제거하여도 원형으로 복원이 가능한 독특한 합성 금속재료이다. 뼈대 구조물에서 변형이 집중이 되는 부위에 기존에 사용된 강재를 대신하여 초탄성 형상기억합금을 사용한다면 시스템의 복원 효과를 극대화 시킬 수 있다. 따라서 본 연구는 내진성능이 우수한 좌굴방지 가새프레임에 초탄성 형상기억합금 소재를 접목시킨 새로운 구조 시스템을 제안하고 자 한다. 본 연구에서 제안된 구조시스템의 성능을 검증하기 위하여 현재 사용되는 설계코드를 참고하여 6층의 가새프레임 빌딩을 설계를 하고 2차원적인 유한요소 프레임 모델에 각각의 지진 위험도 레벨의 가속도 데이터를 사용하여 비선형 동적 해석을 실시하였다. 해석결과를 바탕으로 초탄성 형상기억합금 가새시스템을 사용한 프레임 구조물과 기존의 가새시스템을 성능적인 측면에서 서로 비교하였다. 해석결과는 지진하중 이후에 초탄성 형상기억합금 가새시스템은 구조물에 잔류 처짐을 감소하는데 매우 효율적임을 보여주고 있다. The researches have recently progressed toward the use of the superelastic shape memory alloys (SMAs) to develop new smart control systems that reduce permanent deformation occurring due to severe earthquake events and that automatically recover original configuration. The superelastic SMA materials are unique metallic alloys that can return to undeformed shape without additional heat treatments only after the removal of applied loads. Once the superelastic SMA materials are thus installed at the place where large deformations are likely to intensively occur, the structural system can make the best use of recentering capabilities. Therefore, this study is intended to propose new buckling-restrained braced frames (BRBFs) with superelastic SMA bracing systems. In order to verify the performance of such bracing systems, 6-story braced frame buildings were designed in accordance with the current design specifications and then nonlinear dynamic analyses were performed at 2D frame model by using seismic hazard ground motions. Based on the analysis results, BRBFs with innovative SMA bracing systems are compared to those with conventional steel bracing systems in terms of peak and residual inter-story drifts. Finally, the analysis results show that new SMA bracing systems are very effective to reduce the residual inter-story drifts.

A simple hybrid damping device with energy-dissipating and re-centering characteristics for special structures

The usage of special materials with unique properties in seismic resistant structures has increased since the 1994 Northridge earthquake to overcome limited energy dissipation and ductility. Among them, shape memory alloy (SMA) is a unique metallic alloy that has the ability to undergo large deformations and revert back to its original un-deformed shape. Thus, a simple and practical hybrid damping device equipped with SMA that provides both energy-dissipating and re-centering (strain-recovering) capabilities is developed and evaluated in the present paper. Quasi-static loading tests on Nitinol bars are conducted to obtain their mechanical properties in tension and compression. The optimum proportion of SMA and steel in the device is achieved through analyzing various models. Placing the proposed device in semi-rigid bracing members of special structures will localize the energy-dissipating and ductility while providing the brace with strain-recovering capability. Copyright © 2012 John Wiley & Sons, Ltd.

Response modification factor of steel frames utilizing shape memory alloys

Shape memory alloys are unique metallic alloys that have the ability to undergo large deformations while reverting back to their original undeformed shape, which provides recentering capabilities to the braced frame. In this article, the seismic response of steel braced frames employing shape memory alloy braces is evaluated. The research is carried out by investigating the overall behavior of the structural system as well as taking a close look at response of the system by examining the modification factors of the system. Static pushover analysis, incremental nonlinear dynamic analysis, and linear dynamic analysis are performed in order to investigate the overstrength, ductility, and response modification factors in the structural steel frames. The effects of building height, number of spans, and different types of bracings including diagonal X and Chevron are considered. Comparing the response modification factor of different system configurations indicates that the seismic response of Chevron bracing is preferable when compared with other types of bracings.

Component Mode Synthesis Using Undeformed Interface Coupling Modes to Connect Soft and Stiff Substructures

Classical component mode synthesis methods for reduction are usually limited by the size and compatibility of the coupling interfaces. A component mode synthesis approach with constrained coupling interfaces is presented for vibro-acoustic modelling. The coupling interfaces are constrained to six displacement degrees of freedom. These degrees of freedom represent rigid interface translations and rotations respectively, retaining an undeformed interface shape. This formulation is proposed for structures with coupling between softer and stiffer substructures in which the displacement is chiefly governed by the stiffer substructure. Such may be the case for the rubber-bushing/linking arm assembly in a vehicle suspension system. The presented approach has the potential to significantly reduce the modelling size of such structures, compared with classical component mode synthesis which would be limited by the modelling size of the interfaces. The approach also eliminates problems of nonconforming meshes in the interfaces since only translation directions, rotation axes and the rotation point need to be common for the coupled substructures. Simulation results show that the approach can be used for modelling of systems that resemble a vehicle suspension. It is shown for a test case that adequate engineering accuracy can be achieved when the stiffness properties of the connecting parts are within the expected range of rubber connected to steel.

Component Mode Synthesis Using Undeformed Interface Coupling Modes to Connect Soft and Stiff Substructures

Classical component mode synthesis methods for reduction are usually limited by the size and compatibility of the coupling interfaces. A component mode synthesis approach with constrained coupling interfaces is presented for vibro-acoustic modelling. The coupling interfaces are constrained to six displacement degrees of freedom. These degrees of freedom represent rigid interface translations and rotations respectively, retaining an undeformed interface shape. This formulation is proposed for structures with coupling between softer and stiffer substructures in which the displacement is chiefly governed by the stiffer substructure. Such may be the case for the rubber-bushing/linking arm assembly in a vehicle suspension system. The presented approach has the potential to significantly reduce the modelling size of such structures, compared with classical component mode synthesis which would be limited by the modelling size of the interfaces. The approach also eliminates problems of nonconforming meshes in the interfaces since only translation directions, rotation axes and the rotation point need to be common for the coupled substructures. Simulation results show that the approach can be used for modelling of systems that resemble a vehicle suspension. It is shown for a test case that adequate engineering accuracy can be achieved when the stiffness properties of the connecting parts are within the expected range of rubber connected to steel.

Experimental Investigation of Mechanical Properties of Nitinol, Structural Steel, and Their Hybrid Component

Usage of special materials with unique properties in seismic resistant structures has increased to overcome their limited energy dissipation and ductility as a result of the 1994 Northridge earthquake. Among them, shape memory alloy (SMA) is a unique metallic alloy that has the ability to undergo large deformation while reverting back to its original undeformed shape; but because any new technology has its pros and cons together, using SMA in structures is not all benefit. In this paper, advantages and disadvantages of using shape memory alloys in structures are studied according to experimental results. Monotonic and cyclic static loading tests on Nitinol and steel bars are conducted to obtain their mechanical properties in tension and compression. Also, a comparative low-cycle fatigue test is conducted using steel and Nitinol samples. Considering the results, a simple and practical solution is developed to overcome some of the deficiencies of these two materials in seismic resisting structures.

Towards Inverse Form Finding Methods for a Deep Drawing Steel DC04

A challenge in the design of functional parts in metal forming processes is the determination of the initial, undeformed shape such that under a given load a part will obtain the desired deformed shape. An inverse mechanical or a shape optimization formulation might be used to solve this problem, which is inverse to the standard kinematic analysis in which the undeformed shape is known and the deformed shape unknown. The objective of the inverse mechanical formulation aims in the inverse deformation map that determines the (undeformed) material configuration, where the spatial (deformed) configuration and the mechanical loads are given. The shape optimization formulation predicts the initial shape in the sense of an inverse problem via successive iterations of the direct problem. In this paper, both methods are presented using a formulation in the logarithmic strain space. An update of the reference configuration of the sheet of metal during the optimization process is proposed in order to avoid mesh distortions. A first example showed the results obtained with both methods in isotropic hyperelasticity. A second example illustrated a simplified deep drawing computed with the shape optimization formulation in isotropic elastoplasticity. From the undeformed shapes obtained with both methods the deformed shapes are acquired with the direct mechanical formulation. Compared to the target deformed shape a minor difference in node coordinates is found. The computation time is lower with the inverse mechanical formulation in hyperelasticity. The update of the reference configuration in the shape optimization formulation allowed to avoid mesh distortions but increased the computational costs.

A comparison between inverse form finding and shape optimization methods for anisotropic hyperelasticity in logarithmic strain space

AbstractIn this paper an inverse mechanical formulation and a Limited‐Broyden‐Flechter‐Goldfarb‐Shanno method for shape optimization are compared. Both methods deal with the determination of the undeformed shape of an hyperelastic part knowing its deformed configuration and the applied loads. We consider anisotropic hyperelastic materials that are formulated in the logarithmic strain space. Beside the theoretical aspects, we present a numerical example. We established that no difference could be found between the node coordinates on the undeformed sheets computed with both methods. However the convergence to the solution is faster for the inverse mechanical formulation compared to the L‐BFGS algorithm. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Seismic performance of concrete columns reinforced with hybrid shape memory alloy (SMA) and fiber reinforced polymer (FRP) bars

Lack of corrosion resistance of structural steel has resulted in many structural failures. Fiber reinforced polymer (FRP) bar is emerging as a viable solution to replace steel to mitigate corrosion problems. Since FRP is a brittle material, it can bring about catastrophic sudden structural failures. Conversely, post-earthquake recovery of structures is another prime objective for performance based seismic design. Shape memory alloy (SMA) has the unique ability to undergo large inelastic deformation and regain its undeformed shape through stress removal. Here a hybrid reinforced concrete (RC) column configuration is presented in order to reduce permanent damages, and enhance its corrosion resistance capacity where the plastic hinge region will be reinforced with SMA or stainless steel and the remaining regions with FRP or stainless steel rebar. An analytical investigation has been carried out to develop such hybrid RC columns and analyze them under seismic loadings. The results are compared in terms of base shear-tip displacement, base shear demand/capacity ratio, ductility, residual displacement, and energy dissipation capacity to those of a similar RC column reinforced with stainless steel. The results indicate that such corrosion resistant hybridized column can substantially reduce the residual displacement with adequate energy dissipation capacity during earthquakes.

Re‐centring capacity of dual‐steel frames

AbstractCapacity design principles used in modern seismic design codes are deemed to confine plastic deformations to dissipative elements only. In conventional structures, this can be undesirable as the plastic deformations mean damage to structural elements, interruption to building operations and substantial repair works. If these elements are removable and can be replaced, the structure has the ability to return to the initial undeformed shape after an earthquake, provided restoring forces are supplied by part of the structure still within the elastic range. The objective of the present work, which continues the previous research of the authors, is to present a general methodology for designing structures with removable dissipative elements and re‐centring capability. Two applications are also presented.

Two-way reversible shape memory effects in a free-standing polymer composite

Shape memory polymers (SMPs) have attracted significant research efforts due to theirease in manufacturing and highly tailorable thermomechanical properties. SMPs can betemporarily programmed and fixed in a nonequilibrium shape and are capable of recoveringthe original undeformed shape upon exposure to a stimulus, the most common beingtemperature. Most SMPs exhibit a one-way shape memory (1W-SM) effect since oneprogramming step can only yield one shape memory cycle; an additional shape memorycycle requires an extra programming step. Recently, a novel SMP that demonstrates both1W-SM and two-way shape memory (2W-SM) effects was demonstrated by one of theauthors (Mather). However, to achieve two-way actuation this SMP relies ona constant externally applied load. In this paper, an SMP composite where apre-stretched 2W-SMP is embedded in an elastomeric matrix is developed. Thiscomposite demonstrates 2W-SM effects in response to changes in temperaturewithout the requirement of a constant external load. A transversal actuation of ∼ 10% of actuator length is achieved. Cyclic tests show that the transversal actuation stabilizesafter an initial training cycle and shows no significant decreases after four cycles. A simpleanalytic model considering the programming stress and actuator dimensions is presentedand shown to agree well with the transverse displacement of the actuator. The model alsopredicts that larger actuation can be achieved when larger pre-stretch of 2W-SMP is used.The scheme used for this polymer composite can promote the design of new shape memorycomposites at micro- and nano-length scales to meet different application requirements.

Case Studies of Seismic Vibration Control of Civil Structures Using Shape Memory Alloys

Shape memory alloys (SMAs) are unique class materials that have the ability to undergo large deformations, while returning to their undeformed shape through either the applications of heat (SME) or removal of stress (SE). The unique properties lead to their wide applications in the biomedical, mechanical, aerospace, commercial industries, and recently in civil engineering. The paper presents two case studies of structural seismic vibration control using SMAs. The first one is a study of the SMA reinforced RC members. Two innovative applications in RC members, such as SMA-based Precast Concrete Frame Connection (SMA-PCFC), and SMA reinforced RC short column, were proposed. Moreover, the self-rehabilitation properties of SMAs-based Intelligent Reinforced Concrete Beams (SMA-IRCBs) were further experimentally investigated. The results show that SMAs can improve the mechanical properties of concrete members. SMA reinforced RC members have unique seismic performance compared to ordinarily steel reinforced concrete members. The second one is a study of the structural energy dissipation system using SMAs damping device. An innovative hybrid SMAs friction device (HSMAFD) which consists of pre-tensioned superelastic SMA wires and friction devices (FD) was presented. The results of cyclic tensile tests show that the HSMAFD exhibits stable large energy dissipation capacity and re-centering feature. The effectiveness of the HSMAFD in reducing horizontal response of structures subjected to strong seismic excitations was verified through shaking table tests carried out on a reduced-scale symmetric steel frame model with and without the HSMAFD.

Development of corrosion-free concrete beam–column joint with adequate seismic energy dissipation

The use of Fibre-Reinforced Polymer (FRP) as reinforcement in concrete structures has received much attention owing to its higher resistance to corrosion compared to that of regular steel reinforcement. Since FRP is a brittle material, its use in seismic resisting structural elements has been a concern. FRP RC structures can be made ductile by utilizing a ductile material such as steel at the plastic hinge regions. However, the use of steel negates the corrosion resistance purpose of FRP. On the other hand, Nickel–Titanium (Ni–Ti) shape memory alloy (SMA) is highly resistant to corrosion. It also brings about an added advantage in seismic regions since it has the unique ability to undergo large deformation, but can regain its undeformed shape through stress removal. In this study, a SMA–FRP hybrid RC beam–column joint has been proposed to address not only corrosion resistance, but also seismic related problems. This joint is reinforced with a super-elastic Ni–Ti SMA bar at the plastic hinge regions of the beam and FRP in the other regions of the beam and column. To validate the proposed joint, an experimental investigation has been carried out to develop such a joint and test it under reversed cyclic loading. The results are compared in terms of load–storey drift, moment–rotation and energy dissipation capacity to those of a similar RC beam–column joint specimen reinforced with conventional steel. The SMA–FRP beam–column joint proved to have adequate energy dissipation under earthquake type loading.

A General Methodology for the Determination of 2D Bodies Elastic Deformation Invariants: Application to the Automatic Identification of Parasites

A novel methodology is introduced here that exploits 2D images of arbitrary elastic body deformation instances so as to quantify mechanoelastic characteristics that are deformation invariant. Determination of such characteristics allows for developing methods offering an image of the undeformed body. General assumptions about the mechanoelastic properties of the bodies are stated which lead to two different approaches for obtaining bodies' deformation invariants. One was developed to spot a deformed body's neutral line and its cross sections, while the other solves deformation PDEs by performing a set of equivalent image operations on the deformed body images. Both of these processes may furnish a body-undeformed version from its deformed image. This was confirmed by obtaining the undeformed shape of deformed parasites, cells (protozoa), fibers, and human lips. In addition, the method has been applied to the important problem of parasite automatic classification from their microscopic images. To achieve this, we first apply the previous method to straighten the highly deformed parasites, and then, apply a dedicated curve classification method to the straightened parasite contours. It is demonstrated that essentially different deformations of the same parasite give rise to practically the same undeformed shape, thus confirming the consistency of the introduced methodology. Finally, the developed pattern recognition method classifies the unwrapped parasites into six families, with an accuracy rate of 97.6 percent.

Preform design for forging and extrusion processes based on geometrical resemblance

Preform design in multi-stage forging processes is critical to ensure the production of defect-free parts. Moreover, owing to the geometry and material-flow complexities in forging processes, finding the optimal preform shapes could be difficult and time consuming. This paper proposes an efficient preform design methodology based on geometrical resemblance, which requires several finite element analysis simulation iterations to obtain a good preform shape. The initial and subsequent simulations are carried out by constructing a slightly larger part that geometrically resembles the desired part. Initial finite element analysis simulation of the larger part is performed with a reasonably guessed preform shape, whose forming defects or flash formation would be corrected in subsequent steps. Then a series of intermediate parts of similar shape and between the largest part and the desired part in size are constructed. The undeformed shape corresponding to an intermediate part can be obtained by backwards tracing of material flow from the simulation results of the larger part. This undeformed shape is then taken as the preform shape of the intermediate part. The procedure is repeated until the intermediate part is geometrically close to the desired part, which leads to the preform shape. In order to verify this preform-design methodology, several case studies on forging and extrusion processes have been carried out. The methodology has been shown to be computationally efficient, requiring as few as three finite element iterations to obtain a good preform shape.

Flight Dynamics of High Aspect-Ratio Flying Wings: Effect of Large Trim Deformation

Analysis of flight dynamics of conventional airplane configurations usually begins with a rigid body approximation of the undeformed airplane structure. However, for high aspectratio flying wing configurations, static aeroelastic eects generate significant structural deformation and thus the aircraft configuration in flight is significantly dierent from the initial undeformed shape. As a consequence, flight dynamic studies conducted on a rigid body model based on the initial undeformed structure do not give an accurate assessment of the behavior of the airplane in flight. To overcome this, the deformed shape generated when the flying wing is subjected to static aeroelastic forces at trim, is used to define the rigid body configuration used for flight dynamic analysis. This paper studies the flight dynamic characteristics of the new rigid body configuration in relation to those of the rigid undeformed flying wing, and in relation to the stability characteristics of the complete aeroelastic model. The flight dynamic roots and the stability boundaries of the statically deformed rigid body configuration and the complete aeroelastic model are compared. It is found that staic aeroelatic deformation has a significant influence on the flight dynamic characteristics of high aspect-ratio HALE configurations.

Experimental Investigation on the Seismic Behavior of Beam-Column Joints Reinforced with Superelastic Shape Memory Alloys

Superelastic Shape Memory Alloys (SE SMAs) are unique alloys that have the ability to undergo large deformations and return to their undeformed shape by removal of stresses. This study aims at assessing the seismic behavior of beam-column joints reinforced with SE SMAs. Two large-scale beam-column joints were tested under reversed cyclic loading. While the first joint was reinforced with regular steel rebars, SE SMA rebars were used in the second one. Both joints were selected from a Reinforced Concrete (RC) building located in the high seismic region of western Canada and designed and detailed according to current Canadian standards. The behavior of the two specimens under reversed cyclic loading, including their drifts, rotations, and ability to dissipate energy, were compared. The results showed that the SMA-reinforced beam-column joint specimen was able to recover most of its post-yield deformation. Thus, it would require a minimum amount of repair even after a strong earthquake.

Intraplate deformation adjacent to the Macquarie Ridge south of New Zealand—The tectonic evolution of a complex plate boundary

The distribution of relocated seismicity and the evolving shape of fracture zones through time in the oceanic crust of the Australian Plate adjacent to the Australia:Pacific plate boundary south of New Zealand are used to constrain the deformation of this region of the Australian Plate, here called the Puysegur Block. Relocated seismicity reveals a broad distribution of earthquakes in the Puysegur Block on both inter- and intraplate structures, including two great (M8+) earthquakes in the region over the past twenty years, one of which occurred over 130 km from the plate boundary. Plate reconstructions from the Late Oligocene through Early–Mid Miocene allow us to determine the undeformed shape of fracture zones in the Puysegur Block, formed during the Paleogene when the plate boundary was dominantly a divergent mid-ocean ridge system. Comparing these reconstructions to the present-day shape of the fracture zones allows us to map the deformation that has occurred within the Puysegur Block since the fracture zones formed. These two sets of independent observations delineate a broad zone of deformation extending ~ 150 km into the plate interior from the Macquarie Ridge Complex, the modern plate boundary structure through the region. The persistence of this deformation through time indicates a link with the evolution of the plate boundary over the past ~ 25 Ma from divergence to translation and subduction of the Australian Plate further north at the Puysegur Trench. We infer that this deformation may be a result of stresses in the Puysegur Block resulting from the impingement of the subducting plate on the thickened lithosphere of southern New Zealand. Such a collision may resist subduction, and if resistance remains substantial, further deformation internal to the Puysegur Block may lead to a southward migration of the Australia:Pacific subduction interface and the capturing of this section of lithosphere onto the Pacific Plate.