Comparative Mechanical Study of Pressure Sensitive Adhesives over Aluminium Substrates for Industrial Applications.

The use of adhesives for fixing low-weight elements is showing increasing interest in the industry, as it would reduce the weight of the assembly, costs, and production time. Specifically, the application of pressure-sensitive adhesives (PSAs) to join non-structural naval components to aluminium substrates has not yet been reported. In the present work, a study of the mechanical behaviour of different double-sided PSAs applied on bare aluminium alloy substrates is performed. The influence of surface roughness, surface chemical treatments, and the matrix of the adhesives is studied through different mechanical tests, such as shear, T-peel, and creep. The application of an adhesion promoter improved the mechanical behaviour. Low roughness substrates provided better performance than ground samples. Acrylic foam adhesives were subjected to creep tests, whose results were fitted to a simple mathematical model, predicting the fracture time as a function of the applied load.

Creep Testing of Thermoplastic Fiber-Reinforced Polymer Composite Tubular Coupons.

Thermoplastic fiber-reinforced polymer composites (TP-FRPC) are gaining popularity in industry owing to characteristics such as fast part fabrication, ductile material properties and high resistance to environmental degradation. However, TP-FRPC are prone to time-dependent deformation effects like creep under sustained loading, which can lead to significant dimensional changes and affect the safe operation of structures. Previous research in this context has focused, mainly, on testing of flat coupons. In this study, a creep testing method for TP-FRPC tubular coupons was developed. Specimens were fabricated using tape winding and subjected to well-defined loading conditions, i.e., pure hoop tensile and pure axial compressive stress. Strain gauges and digital image correlation were both employed for strain measurements and were found to be in good agreement. The evolution of strain rate, Poisson's ratio and creep compliance were investigated. The prediction of experimental data by the Burgers model and the Findley's power law model were explored. The research findings suggest that the developed experimental and analysis approach provides valuable information for the design of material systems and structures.

The Influence of Process Parameters and Build Orientation on the Creep Behaviour of a Laser Powder Bed Fused Ni-based Superalloy for Aerospace Applications.

Additive Layer Manufacturing (ALM) is an innovative net shape manufacturing technology that offers the ability to produce highly intricate components not possible through traditional wrought and cast procedures. Consequently, the aerospace industry is becoming ever more attentive in exploiting such technology for the fabrication of nickel-based superalloys in an attempt to drive further advancements within the holistic gas turbine. Given this, the requirement for the mechanical characterisation of such material is rising in parallel, with limitations in the availability of material processed restricting conventional mechanical testing; particularly with the abundance of process parameters to evaluate. As such, the Small Punch Creep (SPC) test method has been deemed an effective tool to rank the elevated temperature performance of alloys processed through ALM, credited to the small volumes of material utilised in each test and the ability to sample material from discrete locations. In this research, the SPC test will be used to assess the influence of a number of key process variables on the mechanical performance of Laser Powder Bed Fused (LPBF) Ni-based superalloy CM247LC. This will also include an investigation into the influence of build orientation and post-build treatment on creep performance, whilst considering the structural integrity of the different experimental builds.

Static viscoelastic properties of bionic UHMWPE articular cartilage material / 医用生物力学

Objective To evaluate the static viscoelastic properties of the porous gradient UHMWPE material by the creep, stress relaxation and creep recovery tests. Method The porous gradient UHMWPE material was prepared by the template leaching (T-L) method. The porous structure was characterized by scanning electron microscopy(SEM) and the porosity and pore distribution of porous layer were measured by a pressure mercury analyzer. The creep, stress relaxation and creep recovery properties were tested by the experimental determination of flat indentation. Results The porous layer of T-L UHMWPE was well bonded with the substrate material. With the increase of NaCl content, the porosity and pore size distribution scope improved clearly. Creep deformation and modulus presented a nonlinear increase with time and the stress and modulus of stress relaxation showed a nonlinear decrease with time. The buffering capacity for impact loads of porous gradient UHMWPE was significantly higher than the compact UHMWPE. Experimental results showed that the creep recovery properties of the reasonable porosity of U50 and U60 samples were almost similar to the compact UHMWPE material. But the higher porosity caused the increase of the plastic deformation. Conclusions The porous structure of UHMWPE effectively increased the elastic property and strain response sensitivity, which may be beneficial to improve the lubrication of frictional contact surfaces and reduce the wear of artificial joints.