紫禁城传心殿油饰彩画环境致裂机理及病害演化路径研究OA

To address the widespread issues of cracking,flaking,and delamination of the exterior polychrome decorations and column oil-painted coatings of the Chuanxin Hall in the Forbidden City under complex outdoor environments,this study integrated long-term environmental monitoring,mi-croscopic cross-sectional analysis,compositional testing,and nanomechanical characterization to sys-tematically reveal the cracking processes and damage evolution mechanisms of multilayer coatings un-der natural exposure conditions.The results indicated that:(1)both the polychrome decorations and oil-painted coatings exhibited a typical stratified structure of"dense thin pigment layer over a porous and heterogeneous ground layer,"with the interlayer interface forming a natural mechanical weak plane.Among these,the ground layer,characterized by developed pores,weak cementation capacity,and dispersed mechanical properties,was an internal sensitive zone where microcracks preferentially initiated.(2)The elastic modulus of the ground layer varied by orders of magnitude across different re-gions.Under hygrothermal environmental fluctuations,this easily caused significant non-uniform de-formation,providing mechanical conditions for the accumulation of interfacial damage.(3)It was found that environmental actions such as temperature-humidity cycling,rainfall infiltration,and light-induced aging continuously drove the degradation of the coating performance through repeated loading.Among them,the wet expansion-dry shrinkage effect induced by humidity variations was the most crit-ical,which significantly amplified the interfacial stress due to the moisture absorption and expansion of the ground layer,thereby accelerating the progressive destabilization of the multilayer structure.(4)A continuous deterioration pathway of"environmental driving-material response-interfacial instability-macroscopic delamination"was established,elucidating the intrinsic mechanisms of the evolution of coating deterioration from microscopic damage to macroscopic delamination.From the perspective of disaster prevention and mitigation,the continuous degradation process of multilayer coatings essential-ly delineates a disaster evolution pathway driven by environmental hazard factors and progressively am-plified through material-and interface-level responses,ultimately resulting in the systemic failure of protective functions of the coating and posing a potential risk to the long-term safety performance of historic timber structures.