Analysis of mechanical strengths of extreme line casing joint considering geometric, material, and contact nonlinearities

To address the challenges associated with difficult casing running,limited annular space,and poor cementing quality in the completion of ultra-deep wells,the extreme line casing offers an effective solution over conventional casings.However,due to its smaller size,the joint strength of extreme line casing is reduced,which may cause failure when running in the hole.To address this issue,this study focuses on the CST-ZTΦ139.7 mm×7.72 mm extreme line casing and employs the elastic-plastic mechanics to establish a comprehensive analysis of the casing joint,taking into account the influence of geometric and material nonlinearities.A finite element model is developed to analyze the forces and deformations of the extreme line casing joint under axial tension and external collapse load.The model investigates the stress distribution of each thread tooth subjected to various tensile forces and external pressures.Additionally,the tensile strength and crushing strength of the extreme line casing joint are determined through both analytical and experimental approaches.The findings reveal that,under axial tensile load,the bearing surface of each thread tooth experiences uneven stress,with relatively high equivalent stress at the root of each thread tooth.The end thread teeth are valuable spots for failure.It is observed that the critical fracture axial load of thread decreases linearly with the increase of thread tooth sequence.Under external pressure,the circumferential stress is highest at the small end of the external thread,leading to yield deformation.The tensile strength of the joint obtained from the finite element model exhibits a relative error of less than 7%compared to the analytical and experimental values,proving the reliability of the finite element model.The tensile strength of the joint is 3091.9 k N.Moreover,in terms of anti-collapse capability,the joints demonstrate higher resistance to collapse compared to the casing body,which is consistent with the test results where the pipe body experiences collapse and failure while the joints remain intact during the experiment.The failure load of the casing body under external collapse pressure is 87.4 MPa.The present study provides a basic understanding of the mechanical strengths of extreme line casing joint.

Advances in the biological function of interleukin 38 and its study in immune diseases

IL-38 is a newly discovered anti-inflammatory cytokine that belongs to the IL-1 family's IL-36 subfa+mily.Nonetheless,recent studies have shown that it can interact with multiple receptors to impede downstream signaling pathway activation,thereby restraining the differentiation and maturation of Th17 cells.While IL-38 enhances the immunosuppressive activity of Treg by inhibiting the transformation of CD4+T cells to Th17 cells,it can also exert its immune regulatory role by binding to the corresponding IL-38 receptor on the cell surface,which in turn inhibits classical signaling pathways such as NF-κB,P38,or JNK activation.IL-38 has been shown to alleviate disease progression in Rheumatoid Arthritis(RA),Systemic lupus erythematosus(SLE),cardiovascular disease(CVD),and other diseases by reducing the production of inflammatory cytokines and limiting the inflammatory response that is dependent on T cell subsets.Moreover,an increasing body of evidence suggests that IL-38 is a promising therapeutic target for these diseases.This article primarily reviews the immunological function of IL-38 and its involvement in related diseases,providing insights and theoretical support for chronic inflammatory and autoimmune diseases.