An Investigation into the Measurement and Prediction of Mechanical Stiffness of Lower-limb Prostheses used for Running

Two energy return prosthesis are subjected to three different statically applied loading methods. This initial study proposes that statically applied loading to a sport prosthesis using several controlled methods were statistically robust enough to derive a mechanical stiffness value. However, any predicted stiffness is drawn into question when allowing any movement of the distal end. This uncertainty will make any evaluation or prescription of lower-limb prosthesis technology based upon their stiffness incorrect. In addition, the peak calculated stiffness at the expected bodyweight induced ground impact load of a runner is judged the most representative assessment method. This study attempts to build on previous research advocating the need to monitor the performance of prosthesis lower-limb technology in disability sport. Practitioner Summary: This paper extends previous research regarding the fairness of prosthetics technology used in running with a lower-limb amputation. It pilots a quantitative assessment of high activity prosthetics technology and ultimately demonstrates how incorrect assessment can lead to incorrect specification of running prosthesis for elite level spor

The Mechanical Behavior of a 25Cr Super Duplex Stainless Steel at Elevated Temperature

Peer reviewedPostprin

Predviđanje zakrivljenosti bimetalne limene ploče Al-Cu tijekom asimetričnog hladnog valjanja

In the paper, solving a problem of rolling Al-Cu plates by the numerical way is presented. In the development of new technologies in rolling of bimetallic plates there are many problems both with ensuring a uniform strain distribution and producing a straight plate as well. Such a solution within research of the numerical simulation was obtained at the Forge 2 program based on finite element method. The cold rolling process was carried out at the temperature of 20 °C for 10 %, 20 % and 25 % relative rolling reduction. The curvature of bimetallic plate was numerically controlled by changing the speed of one roll. In this article the numerical analysis of asymmetrical rolling processes of plate composed with two metal layers, Al and Cu, has been done. At the work an influence of rotary speed ratio and value deformation on change of curvature bimetallic plate is determined.U radu je predstavljen numerički način rješavanja valjanja Al-Cu limenih ploča. U razvoju novih tehnologija za valjanje bimetalnih ploča ima mnogo problema i u osiguravanju jednolikog rasporeda deformacije i u proizvodnji ravnih ploča. U okviru provedenih istraživanja programa Forge 2, baziranom na metodi konačnih elemenata, ostvarena je numerička simulacija. Proces hladnog valjanja proveden je na temperaturi od 20 °C s relativnom redukcijom valjanja od 10 %, 20 % i 25 %. Zakrivljenost bimetalne ploče kontrolirala se numeričkim mijenjanjem brzine valjaka. U ovom članku napravljena je numerička analiza procesa asimetričnog valjanja ploče sastavljene od dva metal nasloja: Al i Cu. Također je utvrđen utjecaj omjera brzine rotacije i vrijednosti deformacije na promjenu zakrivljenosti metalne ploče

Bimetalni lim St3S+Cu

The paper presents a theoretical analysis of the asymmetrical process of rolling bimetal plates composed of the base St3S layer and a Cu cladding layer. Investigation carried out aimed at determining the curvature of bimetal band depending on the value of roll peripheral speed asymmetry factor av. Computer simulations were performed on three different layer thickness ratios, HS/HH. Numerical studies were based on computer simulations carried out using the Forge 2D software. For computations, this program uses the finite-element method. The asymmetry of the process resulted from a non-uniform distribution of rolling reduction into the bimetal band layers, which caused the band to bend at the rolling mill exit. To counteract this behaviour, an asymmetry of working roll peripheral speeds was introduced.Članak daje teorijsku analizu učinka odnosa debljine sloja bimetalnih limova sastavljenih od osnovnog sloja St3S i sloja presvučenog bakrom. Provedena istraživanja su imala za cilj odrediti zakrivljenost bimetalne trake ovisno o vrijednosti faktora asimetrije av periferne brzine. Izvedene su kompjuterske simulacije tri sloja s različitim omjerima HS/HH debljine. Numeričke studije su se zasnivale na kompjuterskim simulacijama provedenim pomoću softvera Forge 2D. Za izračune, ovaj se program služi metodom konačnih elemenata. Asimetrija procesa rezultira od nejednolikog rasporeda redukcije u slojeve bimetalne trake koje uzrokuju savijanje trake na izlazu iz valjačkog stana. Kao protuteža takvom ponašanju uvedena je asimetrija perifernih brzina radnog valjka

Optimization of Heat Treatment in Aspect of Production's Costs Reducing and Improving of Casting Quality from Duplex Cast Steel

Abstract The paper determines possibilities of cost optimisation in the production of GX2CrNiMoCu25-6-3-3 type duplex cast steel castings through selection of appropriate solution heat treatment temperature, which value depends on the content of alloying elements. Metallographic analysis was carried out for as-cast and heat treated cast steel. Hardness and impact strength of the cast steel were determined, which were correlated with the volume fraction of phases determined by means of ImagePro computer image analyser. It has been shown that increased carbon content creates a need to use higher treatment temperatures, thereby increasing the production cost. With increasing carbon content the cast steel hardness after solution heat treatment increases, however, crack resistance decrease

Solidification structure of massive castings from duplex cast steel,

SUMMARY Problems related with duplex massive cast production are presented in this work. Macro and microstructure investigations of GX2CrNiMoCu25-6-3-3 cast steel after solidification were done. The influence of cooling rates and segregation on intermetallic phases formation, especially sigma phase, were shown. The segregation process and cooling rates during solidification have great influence on intermetallic phases formation. Sigma phase occurrence in the cast structure causes deterioration of technological and functional properties